oscarach

The 1/4 wave did make a big difference. Channel 1 & 22 (low power) SWR is now 1.07 car running 1.03 car not running. Channel 22 (high power) SWR is now 1.72 car running 1.65 car not running.

Thanks for the advice, I have ordered a 1/4 wave antenna and will see how that works. I have some aluminum plate laying around and could make a 12"x18" plate bolted to the two load bars and mount the antenna in the middle of that, I assume that would give me a better ground plane. If that would help the antenna work better then a question is does that plate need to be bonded to a vehicle chassis ground? I have seen some of the HAM guys on the off-road forums saying that the ground plane must be connected to a vehicle electrical system ground point and that the antenna must have metal to metal contact with the ground plane, but I have also seen other HAM guys say that is not required so I am confused :-).

Thanks for the information on antenna, I will go look into that. Yep I have the SW-33 as it seemed to be regarded as decent by some of the youtubers. what would be a decent one? I think most of my confusion is around what is a good ground plane. I have read everything from it must be connected a chassis ground point but can just be a bit of angle iron, or the antenna mount must be attached through a large metal surface, or as long as the antenna sits just above a large metal surface. I the case of my placement in the picture do I have any ground plane or just a bad one? Checked and the repeater channels are off by default on the radio, but if I change the power from hi to low on channel 22 the SWR drop to 1.34. I also tried the small magnetic mount antenna in that also came with the radio in the same location and ran the coax the same route and get a SWR or 1.12 across all channels.

I am new to the whole GMRS radio thing and have been finding some conflicting information on the internet. My setup: Midland MXT275 with MXTA25 ghost antenna connected with provided coax cable. The antenna is mounted an antenna bracket that attached to a load bar on a aluminum truck bed cap. The bottom of the antenna sits about 2 inches above the roof of the bed cap. On channels 1 to 7 SWR of 1.46 and 2.1 on channels 16 to 22. So my questions are Will that aluminum roof make a good enough ground plane? If so does the antenna need to be mounted directly to it or is sitting an inch or 2 above it ok? Don't really want to drill holes in the roof. The mounting bracket is painted and I have had people tell me I need to remove the paint where the antenna attaches and also to run a grounding strap from the mount to the vehicle chassis ground, is this really the case? About the only thing everyone agreed on is that the MXA25 is not a great antenna, any recommendation for something to replace that with that is not too tall and will fit on the existing NMO mount?